emma murphy has that part of the story. >> reporter: the thousands, and now the few, in the area between tunisia and libya is deserted. the question that remains unanswered is why? have those wishing to leave done so, or are they being prevented from doing so? just days ago, this was the scene as 200,000 passed through the border gate. yet that changed within hours, and the speed of that change has worried many. how long have you been here for? >> seven days. >> seven days? >> yes. >> so you came across the border seven days ago? >> yes. >> reporter: as he visited the border camp where many of the migrants are now housed, international development secretary andrew mitchell revealed satellite images are now being analyzed for holding camps on the libyan side of the border. >> i'm very concerned because it didn't slow down, so it's an artificial and abrupt stop. we have no idea why that is. we're trying to find out, but at any moment, the number could increase very substantially. >> reporter: the libyan regime know that images of thousands waiting for shelter in tunisia are damaging to the